You can just screw it to the bottom of the base for the removable section, they you only have the two input wires to disconnect
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
BATMAN How do you guys install the Buck converters under the layout? My whole RH/TT lifts out as a unit, can I just screw the converter to a small piece of wood glued to the underside?
How do you guys install the Buck converters under the layout? My whole RH/TT lifts out as a unit, can I just screw the converter to a small piece of wood glued to the underside?
I quickly slapped on a coat of paint over the copper tape, I think it needs a second coat but seeing as how it is just a mock-up I won't bother.
This was taken in daylight at 7volts. I think this will be good, time to get to work on the actual RH install, I wish I had installed the lights before I built the RH.
Brent
"All of the world's problems are the result of the difference between how we think and how the world works."
Hey Brent,
I'm glad that you have solved the problem. The lights look great.
As far as the height is concerned, as long as they can be seen through the windows, I would go with whatever looks good to you.
Thanks for sharing your experiences with the roundhouse lighting. I'm approaching the same point in constructing the roundhouse for the club and I want the lighting to look good. I already have the copper tape on order.
I have to say that I am really tempted to use incandescent bulbs like Mel does. I have never been totally happy with the colour that LEDs give off, and I have tried several different methods of adjusting the colour.
Dave
I'm just a dude with a bad back having a lot of fun with model trains, and finally building a layout!
Thanks Mel.
They in parallel hooked up to the copper tape on each side of the beam. Can those resistors be painted?
Okay here is round two. I need to take some photos when it gets dark with the intensity turned down but so far I am a happy camper. What do you think about how low to hang them, what looks best, 1-2-3 or 4.
You can see the resistors on this side.
The other side.
These were very tiny and somewhat intimidating to work with. With a little practice, it becomes very easy to solder this stuff and it is much more robust than I thought it would be.
I think tomorrow I will paint some sort of glue along the edge of the copper tape as I don't know what time will do to the sticky factor of the tape. I will paint it as well, in fact, the paint may be all the glue it will need. Can those little SMD resistors be painted?
I think tomorrow I will paint some sort of glue along the edge of the copper tape as I don't know what time will do to the sticky factor of the tape. I will paint it as well, in fact, the paint may be all the glue it will need.
Can those little SMD resistors be painted?
Here's one of my initial tests of my nine-stall roundhouse lighting:
RH_lights3 by Edmund, on Flickr
For the general area lighting I used "string lights" cut into seven LED segments and run perpendicular to the stalls. Of course, toward the front there was a little extra wire and toward the back I had to stretch them out.
IMG_4762 by Edmund, on Flickr
I believe the LED spacing is around five inches.
These are SMD LEDs wired in parallel on two epoxy-coated solid copper lines. I simply cut to length and figure the appropriate resistor to give the brightness I desire. They are wired in groups of two so that third wire can be removed after cutting the lengths you want.
IMG_4760 by Edmund, on Flickr
IMG_4766_fix by Edmund, on Flickr
The middle stalls I have added extra lights to illuminate the running gear. I saw this detail on some of the interior photos of roundhouses.
RH_lights4 by Edmund, on Flickr
Then there are the outside goose-neck lamps. In all I believe there are 97 LEDs. I never measured the total current draw.
Good Luck, Ed
RR_MelI would suggest you redo the copper foil on the beams. Put a separate foil tape on each side of the beam, one positive and the other negative. Solder one leg of a 1.2K or 1200Ω â…› watt resistor to one of the foils, doesn’t matter which one but do all of them alike, then solder one wire of your hanging fixture to the other leg of the resistor and the other wire to the opposite foil. This would put the LEDs in parallel keeping the brightness of the LEDs closer to equal.
This is what I had decided to do last night, I can still use the #38 Magnet wire for each individual LED giving it the look I want. I am never averse to starting over and decided a few days ago I would have to, no worries, that's how we learn.
I made the lights and can salvage the shades so the loss of four LEDs is nothing I went through more than that learning to solder the wire to them, they are so small there is quite a learning curve. I am sure they must be damaged after I put them through the wringer.
I plan on using this to control the intensity of the lights. I have a whole bunch of them I ordered from China for $.25 EA. Between these and the dimmer control for the room lights, it will be nice to play around and get the right settings.
Thanks for everyone's help so far, I am sure I'll be back for more.
Two things:
Remember, the rating for a given wire size is the maximum it can safely carry. It doesn't take into account the voltage drop due to wire resistance. At least one chart has #38 at almost .7 ohms per foot. So depending how long the sections of #38 are, you could be significantly increasing the resistance - it will just act like you used a larger than 120 ohm resistor, but unless the LEDs out on really long strings you'd probbaly still be within the tolerance range of the resistor - which BTW I would use slightly bigger that 120, sonce that results in 20ma tot he LEDs and unless you are using precision resistors, one on the small side of the range may put too much current through the LEDs. Actually, if there is a noticeable difference in the brightness of individual strings of 4 LEDs, it could be the resistor itself. You may have to take a bunch and measure them with a meter and pick the 7 that are closest in actual measurement to make it all match up as evenly as possible.
Second - hmm, I forgot my second item - oh, more on the wire size, I think. When you connect loads in parallel, the current adds up, that's why seven groups of 4 LEDs, where each group of 4 draws 20mA, draws 140mA. So you DEFINITELY need thicker wire to feed that, #38 is far too small. Once the roof is in place, can you really see any of that without contorting yourself to a crazy angle to peer up from track level through one of the windows? I know Mel and others have posted using heavier wire as both the current carrying AND support for an array of LEDs over a large area. 2 birds, one stone.
Oh and Mel, using those LEDs as table lamps - amazing! From any normal view they look exactly like table lamps.
Thanks, Mel, I guess my #38 @35mA is too small.
In the first post showing what the array wizard showed, the last line at the bottom says "the array draws a current of 140mA from the source". What size wire should I be using to attach to the LEDs?
Thanks, Randy, what about running the four 3.2v/20ma LEDS through that Magnet wire rated at 35ma? Isn't that why the brightness varies?
No, and the current rating has nothing to do with it. The current rating of an LED is the maximum you can allow through it before it becomes a DED (dark emitting diode). The key parameter for series wiring LEDs is the forward voltage. If the rating is 3.5 volts, and you put 4x in series, the total voltage is 4 x 3.5, 14 volts. You will need a poer supply that puts out more than this. To calculate the current and resistor needed, simply treat the 4 LEDs as one, so now you have a 14V LED. Say you feed it with 16V. For a single LED, you take Vpowersupply and subtract Vled, and use this result and the desired current to calculate the resistor via Ohm's law, solving for R, so R=V/I. I should NEVER be the maximum from the LED rating, and definitely not over it. So we want half, 10ma - so you have your 16V power supply, 14V dropped across the 4 LEDs, leaving 2 volts, divided by 10ma (.010 amps) and you get a 200 ohm resistor. 200 ohms is only a standard value in 5% tolerance which isn't all that common. So you will have to go a little bit larger, for less current, or a little bit smaller, for more current. Either way, since we calculated at 10ma, you have plenty of room to go one size smaller resistor without exceeding the 20ma. For slightly less brightness, use the nearest higher value resistor, for lower current.
Really that's all there is to it. If the LEDs are all matched, with the same forward voltages, then there should be no difference in brightness as each one will drop the same voltage, and the exact same current will flow through each of the 5 devices in series (4 LEDs and the resistor).
Okay, after a quick visit back to my array, I may have had the ultimate DUH! moment. I have four SMD603s in a series, they are rated at 20ma forward each. Does this affect the other LEDs downstream? Also, the #38 Magnet wire is rated at 35ma. I somehow had referenced a different package of wire I had. So am I right in assuming that either or both is the problem?
could it be the twisted magnet wire? soldering the wires may have softened the insulation.
can you try unsoldering one leg of the dimmest LED
Measure the resistance from the ends of the wire where they are soldered in both directions. in one direction, the forward diode direction, it should be low, in the opposite direction it should be infinite. If it's not infinite, then there's a resistive path in parallel with the LED.
try to separate the twisted magnet wires all the way to the LED. See if the resistance become infinite
after separating, see if it is brighter by holding the unsoldered end against the solder pad
greg - Philadelphia & Reading / Reading
rrinker Could be - either overheating them, or a bad joint resulting in an additional resistence. --Randy
Could be - either overheating them, or a bad joint resulting in an additional resistence.
I think the overheating might have been an issue as I was having trouble with the early ones. When I switched from liquid flux to a paste, the paste helped hold the magnet wire in place and I was in and out fast.
What if there is some residual paste on the LED causing a shorting issue, is that possible?
I think I am going to hang some of my later efforts and see if that solves the problem.
What temp should I use to solder the resistors to the copper tape? It seems to take longer for the solder to bond with the resistor than the copper tape even though I am tinning the resistor.
Hi Brent,
As Mel suggested, there shouldn't be that much variance in the voltage across the LEDs. I suspect that the LEDs are themselves the culprit. Where did you get them?
I have two suggestions:
1. Buy some new LEDs from a source that you can trust. 'Wehonest' on eBay usually receives favourable comments on the forums.
2. Forget wiring the LEDs four in series with one resistor. Use a resistor for each LED. Tried and true. Sorry to repeat myself, but if you are like me and don't understand the intricacies of electronics, then do what works.